Control mechanism



Patented Sept. 29, 1936 l UNITED STATES PATENT OFFICE CONTROL MECHANISM Leonard. C. Hanson, Colonial Heights, Va., as-

signor to Atmospheric Nitrogen Corporation, New York, .N. 2., a corporation of New York Application October 25, 1930, Serial No. 491,207 3 Claims. (Cl. 137-68) This invention relates to control apparatus, and librium with the lower level of liquid in the tower more particularly to control apparatus for mainand the reduced discharge from the tower. No attaining the level of liquid in a vessel at a height tempt is made to restore the liquid level in the which varies in proportion to the flow through the vessel to its original point, but instead, the con- 5 vessel. The invention is particularly applicable trol functions to bring the control responsive eleto apparatus in which rapid fluctuations of liquid ments into equilibrium with each new level in level are encountered; such, for example, as the vessel and with a corresponding discharge scrubbers, coolers and other apparatus employed therefrom. Hence, this control is particularly apin the synthesis of ammonia. plicable to vessels in which rapid fluctuations. of

One object of this invention is to provide a conlevel are encountered'since the control responsive 1o trol apparatus which operates to maintain the liqelements are sensitive to each succeeding flucuid level Within the Vessel at a height which is a tuation and causean increase or decrease in the function of conditions within the vessel; such as discharge, depending on whether the level rises or flow, pressure, density and viscosity. In a vessel falls, respectively. Other objects and advantages having an inlet and outlet pipe, a valve in the outof this invention will appear from the following 15 let pipe, a liquid level within the vessel, a liquid of detailed description.

definite density and viscosity flowing into the The invention comprehendstheprocess for contower at a specified rate and a definite pressure trolling liquid level within a vessel, which involves within the tower, it is evident that to hold the maintaining the level at a height which varies liquid level at a specified height, the valve in the proportionally to the flow through said vessel by discharge line from the vessel must occupy a increasing the flow as the level rises and decreasdefinite position; that is to say, the opening ing theflow as the level falls,

through it must have a definite area. Other con- The preferred embodiment of this invention is ditions remaining constant; an increase in the designed to maintainthe liquid levelin a vesflow into the tower wi Cause t e iq evel t sel under pressure, into and from which liquid is rise, and to Stop its rise, the p g 0 the di continuously introduced and discharged at a h e valve would have to be increased. Other height which is not fixed but which varieswith conditions remaining constant; a decrease in the flow through the vessel, preferably by adjust p e r wo l d crea he v l ity hr the ing the flow through the discharge valve in the discharge va v h l v l w uld ri a d t st p discharge line of the vessel. Obviously, however, 30 s e, the Opening through discharge Valve the control may be used to regulate the flow into must be increased. Other conditions remaina vessel as well as to control the flow out of the ing constant; an increase in density of the liquid s el would decrease the velocity through the discharge The control may involve a weigh bottle responv lve, requiring an increase n the p i f the sive to changes in liquid level within the. vessel, 35 valve to limit the rise in liquid level. Other conthe weigh bottle being suspended frornone end ditions remainin the m n i r in vi of a balance beam. Variations of liquid level in 'W 0f the liquid Would reduce the velflcity the vessel cause corresponding variations of'level t u the discharge Valve and qu a d in the bottle, consequently increasing or dimin- 40 tional p n f h v v to p the r i qishing the effective weight of the bottle, and thus 40 d ev Changes in y Of t ab v 6011- rocking the end of the balance beam carrying ditions in a contrary sense would cause a lowering the bottle either upwardly or downwardly. The of the liquid lei/'61 and would require a Closing o movement of the balance beam controls the operthe valve to stop its flow. Hence, it is evident ation of arelay needle which regulates the movethat the position of the valve controlling the flow ment of a relay piston, in turn governing the 45 from the tower is a function of conditions within operation of a motor capable of exerting the neothe tower. For a rise of liquid level in the vessel essary force for operating the valve in the disor tower, the control functions to increase the discharge line. A spring connected to the balance charge opening and to bring the control responbeam opposes the forces exerted by the weigh sive elements into equilibrium with a new inbottle. Also, suitable linkage connects the relay 50 creased level of liquid in the tower and a new inpiston with the relay needle so that the piston, creased discharge from the tower. Conversely, in its movement caused by the relay needle, rewhen the liquid level falls, the control functions stores the needle to its original position and thus to diminish the discharge opening and to bring brings the mechanism into equilibrium in anew the responsive elements of the control into equiposition corresponding to the changed flow 55 through the discharge valve and the new level in the vessel, as will be more fully described hereinafter.

In the accompanying drawing forming a part of this specification and showing, for purposes of exemplification, a preferred form of this invention without limiting the claimed invention to such illustrative instance, the single figure is a somewhat diagrammatic View, partly in section, of a control apparatus embodying the present invention.

In the preferred form illustrated in the drawing, the invention is shown incorporated in control apparatus for maintaining a level of liquid which varies proportionally to the flow through a vessel subjected to high pressure, and the present description will be confined to the present illustrated embodiment of the invention in such control apparatus. It will be noted, however, that the novel features and improvements are susceptible to other applications, and hence, the scope of this invention is not confined to the improvement herein described.

In the drawing, l 0 indicates the scrubbing tower or other vessel having an inlet line I I through which liquid under pressure, or a mixture of liquid and gas under pressure, passes into the vessel Ill. The discharge line l2 leads to the high pressure side [3 of valve M, which controls the flow from the vessel. The valve 14 will be hereinafter more fully described, and for further disclosure of the structure of the valve, reference may be had to copending application Serial No. 484,259, filed September 25, 1930. If the apparatus is used to control the flow into the vessel, the valve M will, of course, be placed in the inlet line.

Dotted line IS in vessel Ill indicates the height of the level of liquid with which the control apparatus shown in the drawing is in equilibrium. Adapter column l6 has its top connected by tube I! with the top of the tower or vessel Ii! and its base connected by tube l8 with the base of the tower or vessel I I! so that the level of liquid in the adapter column is the same as in vessel H3. The

adapter column provides an indirect connection between weigh bottle l9 and tower or vessel H3. If desired, direct connections between the weigh bottle and the gas and liquid spaces in the vessel may be utilized.

The weigh bottle l9, preferably in the form of a cylinder, has its top connected by flexible tube 2| with the top of the adapter column l6 and its base connected by flexible tube 22 with the liquid space in the column l6. Hence, the level of liquid within the weigh bottle is the same as in the adapter column l6 and in the vessel ID. Weigh bottle I!) is pivoted to one end 24 of balance beam 25. The balance beam is fulcrumed on suitable bearings (not shown), the fulcrum point being indicated by the reference numeral 28. End 29 of the balance beam is provided with an adjustable counterweight 3i and a spring 27 has one end secured to end 29 of the balance beam and the other end fastened to a suitable support indicated at 3B. The spring 2? opposes the forces, i. e., increase or decrease in the effective weight of the bottle, exerted by the bottle on end 24 of the balance beam. Variations of liquid level in the vessel ID, it will be noted, cause corresponding variations of level in bottle I 9, consequently increasing or diminishing the effective weight of the bottle and thus rocking end 29 of the balance beam either upwardly or downwardly against the tension of the spring 21, which maintains the balance beam in its new condition of equilibrium with each change in the effective weight of the bottle 19.

The relay, indicated generally by the reference character A, comprises a relay housing 32 having stepped piston 33-34 therein, the stepped piston being made up of piston 33 and hollow rod 34. The area of the upper surface of the piston 33 bears a definite ratio to the area of the lower surface, preferably it is about one-half the area of the lower surface. The piston 33 remains stationary within the housing 32 only when the pressure of fluid in chamber 35 above the piston 33 bears a definite ratio to the pressure in chamber 36 below the piston 33, depending on the ratio between the areas of the upper and lower surfaces of the piston 33. Chambers 35 and 36 are supplied with pressure fluid, preferably oil, through inlet pipe 38 and inlet orifice 37 respectively, both communicating with the pressure fluid supply line 39.

The inlet orifice 31 is preferably made approximately one-half the area of the outlet orifice 43 hereinafter described. A drop in pressure of the pressure fluid, oil, entering chamber 36 takes place due to its flow through the inlet orifice 3?, the drop in pressure varying as the square of the flow. The pressure within the chamber 36 is controlled by relay needle 4|. The conical pointed end 42 of this needle regulates the discharge through orifice 43 of the chamber 36. With the needle in a definite position with re-- spect to the discharge orifice, in the embodiment herein disclosed, so that the area of the discharge orifice is approximately equal to the area of the inlet orifice, the upward and downward forces on the piston are in equilibrium and the piston 33 remains stationary at a definite point in the relay housing between the top and bottom thereof. Movement of the needle 6! away from this definite position in a downward direction causes end 32 to diminish the discharge through orifice 33, and accordingly, pressure builds up in chamber 36 with consequent upward movement of piston 33 since the equilibrium between upward and downward forces acting on the piston has been disturbed by the movement of the relay needle. As soon as the equilibrium between forces above and below the stepped piston 33 is restored, the piston stops moving. Conversely, upward movement of relay needle 4| by the upward rocking of end 23 of the balance beam away from the aforesaid definite position causes an increase in the escape of pressure fluid through orifice 43 with descent of the piston 33.

The relay needle 4! is pivoted to one end of a lever 44 pivoted at 45 to the balance beam 25. The other end of lever 44 is pivotally connected at 36 with one end of a link il, the other end of which is secured to one end of lever 48 pivoted at 49 to the standard carrying the balance beam 25. It is important to note that the pivot point 33 is directly beneath the fulcrum 23. This permits rocking of the balance beam due to changes in the effective weight of the bottle IS, with corresponding changes in the position of the relay needle, without changing the vertical position of point 46, as will be more fully explained hereinafter. Lever 48 is pivoted to one end of link 5|, the other end of which is suitably pivoted to the top of the piston stem 34.

Pivoted to the body of the piston rod 34, as indicated at 52, is one end of a floating lever 53. The other end of this lever is pivoted, as indicated by the numeral 5%, to the top of the follower 55, A valve stem 56 is associated with an intermediate point on the floating lever. The stem passes through a block 51 integral with, or secured. to, the lever 53. The spring 58 is coiled about the stem 56, one end bears against block and the other end bears against head 59 of the stem 56. A collar 69 on the stem 56 contacts with the block If when it is moved downwardly, imparting this downward motion to the stem 56. A relay or pilot valve 6! involves the usual housing 62 in which valve spool 63 is slidably mounted. Stem 55 is connected with the spool 83 through the ball joint 54.

The relay valve iii is formed with a pressure fluid inlet port G5 communicating with the pressure fluid supply line 65 in turn connected with pressure fluid pipe 39. Port Bl in the valve housing 62 communicates through pipe line 68 with port 65 in the servo motor ll. A drain port 12 in the base of the relay valve communicates with the drain line l3 into which pressure fluid from the discharge orifice also drains. Flange 14 on the valve spool is of an extent sufficient to close the valve port 61, as indicated in the draw ing. Movement of the valve spool downwardly places ports 65 and 61 into communication, resulting in flow of pressure fluid from pipe 66 into ports E5 and El, through pipe 68, into port 69 to servo-motor ll. Movement of the valve spool 63 in an upward direction places port Bl into communication with exhaust port 12 and causes exhaust or pressure fluid from servomotor it into port 59, pipe 68, and ports 5'! and 2?: into drain pipe '53.

Movement of the valve spool 63 is effected through stem 56 and the floating lever 53, which is turn moved by the piston rod 34. Thus, when the stem 34 moves up, it rocks the floating lei r 53 about the pivot point 54, and through g 562, pulls up on stem 55, causing the stem :td connected valve spool E3 to move in an upward direction. When the piston rod 34 descends, it causes downward rocking of lever 53 about the pivot point 54, moving stem and the connected valve spool downwardly through contact of block 51' with collar 5 As above indicated, movement of the piston rod up or down is caused by changes of liquid level in vessel it and weigh bottle l3, which move the relay needle 6! to vary the pressure in chamber 36 below the piston 33.

The servo-motor ll is of sufficient size to exert the necessary forces for moving the valve stem 84 in the valve l4 against the high pressure occurring in chamber 13 of the valve through which liquid from vessel l3 flows into the low pressure chamber 85. The valve stem at is preferably made integral with rod 85, which extends through the low pressure chamber 86 and is suitably secured, as indicated at 88, to the stepped piston 8? within servo-motor H. Discharge line llil leads from the low pressure chamber $6 of the valve to a suitable point of disposal for the liquid flowing from the vessel l9.

Oil is supplied at constant pressure to the small end of the stepped piston 81 of the servomotor through inlet port 9! and pipe 92, which communicates with the supply line The oil pressure on the small end of the stepped piston functions to return the piston when oil is exhausted from the large end. Admission of pressure fluid to the large end of the servo-motor through port 69 causes the servo-motor piston to move to the left as viewed in the drawing, increasing the extent of opening of valve M'and consequently increasing the flow through this valve. Contrariwise, the exhaust. of pressure fluid from the large end of the servo-motor through-port 68 permits the oil pressure on the small end of the stepped piston 81 to force it to the right, diminishing the extent of the valve opening with consequent decrease in flow from vessel ll through valve l4 into the discharge line 85.

The restoring or compensating mechanism associating the servomoter H with the relay A, to prevent over-travel oi the valve stem 84 and further to prevent hunting within the system, will now be described. The restoring mechanism involves a cam 95 having a horizontal surface 85 and an upwardly inclined surface 91'. The camis secured to bracket 53, suitably fastened to stepped piston at 9S, so that the bracket 98 and connected cam 95 reciprocate with the piston 817. Guide roll llll provides a guide and support for the reciprocating cam 95. A cam roller E83, carried by the cylindrical stem I54 slidably guided in housing 165, rides on the cam 95. The base of housing N15 is provided with vertical slots I06, permitting movement of the inclined portion 31 of the cam therethrough. A rod I81, integral therewith or suitably secured to follower I64. extends th-erefrom and is pivoted, as indicated at I68, to the cam rod stem 55. Spring l59, coiled about stem llll', contacts with the top interior of housing I55 and with the cylindrical stem HM and functions to hold the cam roller M33 into engagement with the cam. Movement of the stepped piston toward the left from the piston indicated on the drawing, occasioned by the valve spool 53 being lowered, causes pressure fluid to" flow through ports 65, 6'! and 69 into the servo motor. The stepped piston 8'! therefore moves toward the left, cam 95 moving therewith, and consequently cam roller Hi3 rides up on the inclined surface Bl, causing elevation of stems [84, ill? and raising the floating lever 53 about pivot point 52, restoring the valve spool 63 to its original position. Thus, further introduction of pressure fluid into the servo-motor is prevented,

consequently avoiding over-travel of the valvestem fi l/and hunting within the system. The converse of the above operations takes place when the stepped piston is moved to the right.

The valve seat and stem and the shape of the cam95 is designed, as shown in the drawing, to

prevent wire drawing in the valve l4 and to insure prompt opening of the valve from closed position with gradual movement of the valve once it is opened. The valve seat is formed with a cylindrical portion, indicated at ill, with a conical seating portion l 52. Valve stem 84 comprises a conical seating portion l I3 adapted to register with the seat H2, a cylindrical closing or seating portion H4 of substantially the same diameter as H l and arranged to seat within Ill, and a truncated conical portion H5 in line with and extending from the portion H4. Assuming the valve is in seated position, it will be noted that the high pressure within chamber 13 acts upon the stem and maintains it tightly seated. When the valve stem is moved towards the left, the valve remains closed until the seated portion I M is removed from seat H I, and thus flow through the valve is prevented during the initial opening movement. Continued movement of the stem causes cylindrical portion H4 to leave its seat Ill, permitting flow through the valve; hence, wire drawing does not occur on the seating portions H2 and H3 but are exerted upon the end and is provided of cylindrical portion H4, remote from the seating portion H3.

To permit prompt opening from closed position, the cam 95 is designed with the horizontal surface 96. With the valve stem 84 in seated position, cam roll H33 rests on the surface 96. Initial movement of the stepped piston 81 with consequent movement of cam 95 causes no movement of the cam stem i0 1 due to the fact that the cam does not cause an upward movement of the roller J93. Consequently, the floating lever 53 and the valve spool 63 are not restored; hence, permitting continued flow of pressure fluid into the servomotor and an initial rapid opening movement of the valve l4. Once the valve is opened, the position of the parts is as shown on the drawing, cam roller Hi3 resting on the base of the inclined portion of track 91. Further movement to the left of the servo-motor piston causes the restoring mechanism to operate to prevent over-travel of the valve stem 84.

It will be noted that any motion of the relay piston stem 34 is followed by a corresponding motion of the servo-motor piston H1, and that for each position of the relay piston stem 34, there is a corresponding position of the servo-motor piston 81, and consequently, a corresponding opening of the valve M.

In operation, assume that all of the parts of the control apparatus are in equilibrium, as indicated in the drawing, with a certain flow through the discharge valve, and that oil pressure is being supplied through pressure line 39, and further assume that the flow into vessel It] is increased, this will cause the liquid level to rise in vessel ii], adapter column l6, and weigh bottle I9, increasing the eifective weight of the weigh bottle. It will accordingly descend, causing end 24 of the balance beam to descend about fulcrum 28 and end 29 to ascend about this fulcrum point, slightly stretching the spring 27, the increased tension of the spring opposing the increased weight of the bottle. Pivot point 45 of the lever 24 ascends with the balance beam, causing elevation of the relay needle 4|, permitting oil to escape faster through discharge orifice 43 with consequent diminution of the pressure in chamber 36. Since pivot point it is directly beneath the fulcrum point 28 in the balance beam, there is no relative motion between lever 44* and balance beam 25. The only movement imparted to point 46 by the movement of the balance beam is a slight sidewise motion which is of no consequence.

Due to decrease of pressure in chamber 36, the piston 3-3 and piston stem descend, pulling down the floating lever 53 about the pivot point 54. This moves the valve spool 53 downwardly, causing port 65 to communicate with port 61.

Pressure fluid flows through ports 65 and El from the pressure supply line 39 into pipe 63, port 69 into the servo-motor ll, causing the servo-motor piston 87 to move towards the left and increase the extent of opening of valve l4, hence increasing the discharge from the vessel Ill.

Movement of piston 36 downwardly also causes rod to pull down on pivoted lever 68, which exerts an upward thrust through connecting link 4? on the lever as, turning this lever about point 55, which movement restores the relay needle. Restoration of the needle brings the pressure in chambers 36 and 35 into equilibrium, which causes the piston to rest in its new position in equilibrium with the increased level of liquid in the tower or vessel is, and the increased discharge from the tower, and consequently with the new flow of liquid through the tower.

Upon a further increase in level in the tower til, the operations above described are repeated. The converse of the above operations takes place When the level within the vessel falls. Hence, throughout the operation of the control, it functions to maintain the level in the vessel at a height proportional to the flow through the vessel.

The invention as hereinabove described is embodied in a particular form of construction, but it may be variously embodied within the scope of the following claims.

I claim:

1. Control apparatus comprising in combination, a relay including a piston and a relay needle, links connecting said piston with said relay needle and arranged to return the needle to its original position after each impulse imparted to said needle and means actuated by said relay for effecting control of that which is to be controlled.

2. Control apparatus comprising in combination, a pressure fluid relay housing having a discharge orifice, a relay needle arranged to control the extent of said discharge orifice, a piston within said relay housin and links connecting said piston with said relay needle and arranged to return the needle to its original position after each impulse imparted to said needle.

3. Control apparatus comprising in combination, a pressure fluid relay housing having a discharge orifice, a relay needle arranged to control the extent of said discharge orifice and thereby regulate the pressure within said pressure fluid relay housing, a stepped piston in said housing arranged to be actuated by the pressure fluid within said housing and links connecting said stepped piston with said relay needle and arranged to return the needle to its original position after each impulse imparted to said needle. LEONARD C. HANSON. 

